In her return to Wimbledon Monday morning at the All England Club, Serena Williams defeated Russian Arantxa Rus 7-5, 6-3, in an unexpectedly tight matchup.

Rus, ranked No. 105 in the world, looked at one point like she was capable of pulling off an upset; she was up on Williams early in the second set, but Willams came back. However, Williams also struggled to close out the final game.

Williams won the tournament in 2016, but missed the 2017 tournament while she was pregnant with her first child, born last September.

Williams responds to reports of targeted USADA drug testing

The win in and of itself was no surprise; the biggest early news of the tournament was that Williams acknowledged the recent Deadspin investigation that showed she has been drug tested far more often than other comparable players – including men.

“I never knew that I was tested so much more than everyone else,” Williams said. “Until I read that article I didn’t realize it was such a discrepancy with me as well as against the other players that they listed, at least the American players — both male and female.”

“It would be impossible for me to not feel some kind of way about that,” said Williams, 36. “I just found it quite interesting.”

“How is it I’m getting tested five times? I’m OK with that. Literally verbatim I said: ‘I’m going with that, as long as everyone is being treated equally. That’s all I care about,’” she added

“Tennis has given me so much. It’s such an amazing sport. I feel like equality, that’s all I’ve been preaching, it’s all about equality,” Williams continued. “If that’s testing everyone five times, let’s do it. Let’s be a part of it. It’s just about being equal and not centering one person out. Just due to the numbers, it looks like I’m being pushed out. Just test everyone equally.”

You can watch the full press conference below:

In response to the Deadspin piece, USADA reiterated its policy that it can test athletes whenever it deems appropriate, and communications director Brad Horn responded that there is no reason to believe that Williams is doping.

It’s still unclear at this time, then, why she is being tested such an inordinate amount – unless an involved party is not being transparent.

Williams returned to majors competition in May after taking more than a year off to have her first child. Despite entering unseeded, she won her first three matches of the French Open before withdrawing with a pectoral injury.She was awarded the No. 25 seedfor the Wimbledon tournament, and has recently been outspoken about the need for a maternity leave policy for professional players.